Why are there Primary and Aux SMA Connectors on LTE Enabled Devices?

The two antennas on the main and auxiliary SMA ports will work together to increase data throughput. In addition, the auxiliary antenna also acts as a backup to the main antenna.

Do I need to connect an antenna to the auxiliary SMA connector to connect to a LTE service?
We always recommend connecting both antennas to the SMA ports for better throughput. However, if that is not possible, a single antenna on the Cellular Main SMA connector is enough to connect to a LTE service.

Note: The main antenna is used for transmit, and both Main and Aux antennas are used for receive.